Also on your Wikipedia link it says Norway has a Christian population of 30% to 89.9%...that's too big a range to be accurate in my opinion.
The 7% in Norway are probably the people who actively care about the subject, which doesn't catch all or even most of the people who don't have religious beliefs.
My personal opinion and experience on the matter, is that people who say that they are "christian" in Norway, usually
mean it in the sense that they observe some christian traditions - like baptizing their children, going to church every once in a while on the holidays, getting married in the church and so on. Of all my friends and acquaintances, I can only really think of a single one who's actively religious - and he's a bit kooky.
My view is that in regard to people below 50 years of age, most don't really care about the subject, some label themselves as "spiritual", some as "agnostic" and some as "atheist".
My family is entirely non-religious - at least the members I know well and have contact with regularly.